The present invention relates, in general, to a restraint system for restraining a person in a vehicle of transportation, and more particularly to an arrangement for positioning the shoulder belts of a safety harness in longitudinal direction of legs of a U-shaped shoulder yoke.
Due to the ever increasing speeds in motor sport, especially formula racing, head and neck injuries become more and more common, when a racecar crashes against track barriers or in the event of a collision between two cars. Oftentimes these injuries resulted in catastrophic outcomes such as paralysis or even death. Therefore, head and neck restraining systems have been developed to prevent the head of a driver, in the event of a crash against a standing or moving obstacle, from striking the steering wheel or other cockpit parts. These head and neck supports have been commercialized under the trade name HANS and are described, for example, in U.S. Pat. Nos. 4,638,510 and 6,009,566. These types of head and neck supports include a stiff U-shaped shoulder yoke, which is made of plastic and includes two legs, and a high collar to interconnect the legs. Attached laterally to the collar are tethers which are connected to the helmet of the driver. The tethers have hereby a length that allows a limited mobility of the head during the race.
Secured to the back wall of the cockpit behind the driver are two shoulder belts of a safety harness and routed over the legs of the yoke to a buckle on the chest side of the driver. The leg surfaces confronting the shoulder belts are so constructed as to oppose relative movements of the shoulder belts by a fairly high frictional resistance. When the length-adjustable shoulder belts are taut, the yoke, which conforms to the torso of the driver, is wedged between the torso and the shoulder belts. In the event of a crash, the torso slides into the shoulder belts as a consequence of inertia in acceleration direction, while the yoke remains substantially in the initial position in view of the friction with the shoulder belts so that a shift takes place between the yoke and the torso. Thus, the distance between the collar and the helmet moving in acceleration direction increases. This leads to a tightening of the tethers so that the driver's head is prevented from moving forward in relation to the torso and from striking the steering wheel or other parts of the cockpit. The use of the HANS system is thus able to significantly reduce head and neck injuries.
Helicopter crashes experience substantially vertical retardations which are superimposed only to a limited degree by forward retardation. Oftentimes, the helicopter tilts partially to the side before impacting the ground. While injuries of the lower spinal column during vertical impact have been reduced by the recent development of seats with vertically acting energy converters, injuries to the head have been on the rise as the head bends and can even strike the sternum with the chin. This is especially of concern in military choppers where occupants wear helmets that have a weight of almost 2 kg. Although this situation can be improved through integration of airbags, such systems necessitate a modification of the compartment structure of the helicopter, the arrangement of complicated sensors and the provision of monitoring systems. Costs and added weight thus render this approach economically unviable.
Therefore, the use of a HANS system also for helicopters to protect occupants has been proposed. However, a drawback of the HANS system is the relative distance between the shoulder belts and the occupant's body as the shoulder belts run upon the legs of the yoke. Thus, the shoulder belts have a tendency to slide to the side of the legs because they seek the shortest way from the anchor point at the back wall of a cockpit or a seat structure behind the collar to the chest-side buckle of the safety belt.
An attempt to address this problem involves a closer disposition of the anchor points of the shoulder belts behind the collar. Another approach involves the use of belt straps for the shoulder belts of a width which is smaller than a width of the legs of the yoke. Still another approach involves a particular configuration of the shoulder belts, as disclosed, for example, in German patent publication no. DE 101 14 343 A1. However, for a number of reasons, these various proposals are endowed with drawbacks and shortcomings relating for example to manufacturing techniques or to the effect that is hoped to be obtained but may not always be realized.
It would therefore be desirable and advantageous to provide an improved restraint system to obviate prior art shortcomings and to afford a required freedom of movement of an occupant of a transportation vehicle such as racecar or helicopter, while effectively preventing a sliding of the shoulder belts to the side, even when the shoulder belts move in longitudinal direction relative to the legs of a shoulder yoke.